The problem here is not with the phrase “obviate the need”, which is not redundant, but with the inadequate definition given in the OP’s dictionary. “Obviate” does not mean remove a need, it (usually) means remove, but is only used in contexts when the thing being removed is a need or necessity. (I guess in phrases like “obviate disaster” it also means something like prevent, but, again, its use seems to be limited to certain quite narrow semantic contexts.)
Just Ed’s dictionary, unlike the OP’s, seems to be sensitive to this context dependence of the word’s usage.